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- Jarvis, Erich D., et al.
(författare)
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Whole-genome analyses resolve early branches in the tree of life of modern birds
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 346:6215, s. 1320-1331
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Tidskriftsartikel (refereegranskat)abstract
- To better determine the history of modern birds, we performed a genome-scale phylogenetic analysis of 48 species representing all orders of Neoaves using phylogenomic methods created to handle genome-scale data. We recovered a highly resolved tree that confirms previously controversial sister or close relationships. We identified the first divergence in Neoaves, two groups we named Passerea and Columbea, representing independent lineages of diverse and convergently evolved land and water bird species. Among Passerea, we infer the common ancestor of core landbirds to have been an apex predator and confirm independent gains of vocal learning. Among Columbea, we identify pigeons and flamingoes as belonging to sister clades. Even with whole genomes, some of the earliest branches in Neoaves proved challenging to resolve, which was best explained by massive protein-coding sequence convergence and high levels of incomplete lineage sorting that occurred during a rapid radiation after the Cretaceous-Paleogene mass extinction event about 66 million years ago.
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- Zhang, Guojie, et al.
(författare)
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Comparative genomics reveals insights into avian genome evolution and adaptation
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 346:6215, s. 1311-1320
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Tidskriftsartikel (refereegranskat)abstract
- Birds are the most species-rich class of tetrapod vertebrates and have wide relevance across many research fields. We explored bird macroevolution using full genomes from 48 avian species representing all major extant clades. The avian genome is principally characterized by its constrained size, which predominantly arose because of lineage-specific erosion of repetitive elements, large segmental deletions, and gene loss. Avian genomes furthermore show a remarkably high degree of evolutionary stasis at the levels of nucleotide sequence, gene synteny, and chromosomal structure. Despite this pattern of conservation, we detected many non-neutral evolutionary changes in protein-coding genes and noncoding regions. These analyses reveal that pan-avian genomic diversity covaries with adaptations to different lifestyles and convergent evolution of traits.
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- Venkatesh, Lakshmi Narayanan, et al.
(författare)
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Room temperature and 600 °C erosion behaviour of various chromium carbide composite coatings
- 2019
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 422-423, s. 44-53
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the erosion behaviour of laser clad chromium carbide-Ni rich alloy composite coatings with a wide range of carbide contents at room temperature and 600 °C were investigated. The variation in carbide content of the coatings was due to dilution from the substrate and the high cooling rate in the laser cladding process preventing re-solidification of the molten carbides. Erosion rate was observed to be a function of carbide content alone and was significantly higher at 600 °C as compared to room temperature. Erosion wear ratio (E90/E30) was also dependent on carbide content but decreased at higher temperature and higher carbide contents. A comparison of erosion behaviour with detonation and plasma sprayed counterparts showed the superior performance of laser clad coatings at 600 °C. The poor erosion performance of the detonation and plasma sprayed coatings was due to weak splat bonding. Thick oxide layer formed on the steel substrate after pre-oxidation resulted in its poor erosion performance.
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